Fiber optic cables are presently used in such areas as voice and data transmission in the computer and communications industries. While fiber optic cables are very efficient optically for such uses, leading to low signal losses through the cables, one of the present drawbacks to their use is the complexity of the field termination, that is splicing ends of fiber optic cables. It should be understood that fibers to be connected must be very precisely aligned in an abutting manner, without the presence of such discontinuities as gaps and the like between the end faces of the two fibers. A gap between two end faces causes reflection of the incident light due to the mismatch of the index between the two compounds. That is, air is present within the gaps and rough surfaces which can cause the scattering of the light and attenuation of the signal. Thus, this is the difficulty which presents itself in the field, the preparation of optical fibers for their abutting connection without the use of precisely controllable equipment. Presently, two methods of field termination of plastic core fiber optic cables are utilized.
The first method is to provide a plastic ferrule for insertion of a free end of a fiber optic cable therethrough. The fiber optic cable is glued to the inner periphery of the ferrule and the end of the cable has to be ground down to provide a smooth abutting surface for a similar free end of a mating fiber cable. It should be appreciated that the grinding process is not an easy one to control while in the field without a controlled environment, such as a manufacturing facility where tolerances can be kept to a minimum by the use of high quality machine tools.
A second method is similar to the first method except, rather than grinding the free end of the fiber optic cable, a hot plate is provided by the end user where the hot plate is abutted to the jagged edge of the free end to melt the free end of the fiber optic cable to provide a flat, smooth surface. This method is particularly difficult to carry out as the melting of the plastic fiber must be precisely controlled, otherwise the plastic fiber could be burnt, or damaged by a poorly aligned hot plate. Each of these methods is difficult to carry out in the field in that the surfaces of the fiber optic cables must be finished in a smooth manner and in a square manner relative to the length of the cable for abutment against a mating cable. As mentioned above, it is necessary for two abutting fiber optic cables to be as flush as possible to prevent an air gap between the two cables thereby presenting a difference in index of refraction between the two cables.
A further difficulty is presented where a fiber cable is to be split into two signals, a so-called fiber optic splitter, due to the angles at which the fibers are split, and which the fibers must be terminated.
A method of splitting optical fibers is shown in commonly assigned European Patent Publication Number 0 347 118A, published Dec. 20, 1989, where a splitter housing is formed with a Y-junction for receiving optical fibers. At the intersection of the Y, a gel is disposed which optically connects the fibers together. While the method shown in that patent is acceptable, it has been found that some attenuation is present due to the molding of the Y junction in the housing, between the two adjacent cables. Due to the inability to mold a precise "point" at that section, losses are created.